1. Field of the Invention
This invention relates to an integrated circuit device, and more particularly to an integrated circuit device suitably used for large-scale electronic computers.
2. Description of the Prior Art
In order to obtain an integrated circuit device used for large-scale electronic computers and having very much densely-arranged integrating circuit chips, a plurality of integrating circuit chips are mounted on a multilayer wiring substrate.
This type of integrated circuit device is generally formed by mounting integrated circuit chips, such as LSI chips on one surface of a multilayer wiring substrate, and connecting a feeding conductor, which is provided in the unitarily-formed substrate, and an external power source to each other electrically by a connecting terminal.
As the number of the integrating circuit chips is increased to heighten the mounting density thereof, the sizes of the substrate become large and the substrate temperature increases, so that the substrate readily bends and waves. The specification of Japanese Utility Model Publication No. 32312/1983 published on July 18, 1983, which is entitled "Heat Radiating and Power Supplying Structure for Ceramic Substrates", states that, since the waving or bending of a substrate increases substantially in proportion to the sizes thereof, it becomes very difficult to attach a cooling radiation fin to the substrate by using solder or a bonding agent. It further states that it is difficult in a large-sized substrate to supply an electric current through a feeding conductor therein as in a conventional substrate since the voltage in the feeding conductor drops very greatly. The specification proposes that a feeding conductor be separated from a wiring substrate on which integrated circuit chips are to be mounted. To be concrete, it proposes that insulating sheets having excellent thermal conductivity and mechanical elasticity and feeding conductor plates be laminated alternately and inserted between a wiring substrate (ceramic substrate) and a radiation fin to then fix the resultant product as a whole by bolts. This structure gives rise to problems concerning the contact thermal resistance between the insulating sheets and feeding conductor plates but no reference is made at all to this point. Also, no concrete materials for the insulating sheets having excellent thermal conductivity and mechanical elasticity are disclosed at all.